During production of green tyres on a tyre building production line the corresponding materials are brought to and wound on a tyre building drum. The drum increases its diameter by radial expansion of clamping mechanisms, whereby the bead wires with cores, which have been prepared in advance in a desired position, are pressed on—are clamped to the carcass materials wound on the tyre building drum. The bead wires with cores should stay in this “clamped” position in the course of subsequent technological process of the green tyre production. During the technological process, additional forces are developed which tend to displace the bead wires from the clamped position both in the direction to the drum centre and in the opposite direction. Relatively high clamping force is needed to clamp the bead wires or to ensure their positional stability during the whole subsequent process of tyre production. As a consequence, undesirable deformation of the carcass materials in the nearest vicinity of the place where the bead wire is clamped, leads to negative impacts on the qualitative properties of the product, because particular components have different properties and expand to different diameters. Displacements of carcass materials occur because of impossibility to synchronise ideally the working movements of two clamping mechanisms.
Recently known methods and the respective devices solve the positional stability of the clamped bead wires by means of a suitable form of seating for clamping it, by means of the so called inner rubber membranes or by means of a mechanical rotary bead support.
EP0303197 describes a method of fitting the bead core rings and a tyre assembling machine comprising a winding drum with variable diameter, two attachable lateral parts arranged in a line, at least one of them being displaceable, and a mechanism for adjusting the bead cores which mechanism is arranged at both ends of the winding drum and adapted for coaxial movement relative to the winding drum. The bead core fitting device comprises a circular holder for accommodating a corresponding bead core ring. The circular holders consist of radially displaceable segments, which are disposed concentrically relative to the winding drum axis. The device further contains sliding rings which are located in a plane parallel to the end faces of the winding drum and concentrically relative to the drum axis, and are able to move axially over the circular holders, when the latter are positioned in a line with the end faces of the winding drum.
Subject-matters of WO98/52740 and WO01/68356 are tyre building drums with a turn-up device for production of unvulcanized tyres, consisting of a central axis and two circular segments arranged around an axis to support the bead cores, means for radial expansion of those parts of the tyre components which are situated between the circular segments. The drum being at the other side, outside the circular segments, provided with two sets of hinged arms, which a re able to move axially and to expand radially and are, at the end adjacent to the circular segments, provided with rollers for turning-up those tyre components, which are located at the outer side of the circular segments. The circular segments are spaced apart of each other at a certain distance, while each of them consists of several parts. Each part of the circular segments is provided at its inner side, i. e. in the space between the circular segments, with an inner support for the bead core. The inner support for the bead core is pivotally joined with the respective segment part and during the operation of turning-up it lifts and supports the bead wire from the inner side, thus preventing its displacement inwards between the circular segments.
Any of these known solutions either prevents displacement of the bead wires during the tyre production insufficiently or can be utilized only at a certain type of a building drum. For example, the solution according to WO98/52740 can not be used with the building drums having a fixed central part, because they do not provide enough space for rotating the inner support for supporting the bead wire in the course of production.